1. Field of the Invention
The present invention relates to a guideway type vehicle having a vehicle body and a bogie supporting the vehicle via a bolster spring, such as a guideway type vehicle with rubber tires, in which the height adjustment thereof is made easy by performing a high-sensitive measurement of the height of the vehicle body which changes in response to the change of the vehicle body weight.
2. Description of the Related Art
A new transportation system as a medium-capacity transportation using rubber tires traveling on a special guideway such as a new transit system and MRT, has become popular in recent years. This transportation system is usually fully automated. In some cases, the transportation system is equipped with guide wheels being guided on a guideway.
In this transit system, the vehicle such as a train uses an air spring as a bolster spring. The bogie supports the vehicle body via the air spring and thus the height of the vehicle body changes in response to the weight change of the vehicle body (change of the number of passengers). To keep the floor level of the vehicle constant, a height adjusting mechanism is adopted.
The height adjustment mechanism is explained in reference to FIG. 5 and FIG. 6. In FIG. 5 and FIG. 6, a vehicle 100 of the new transit system has a bogie 104 mounted under a vehicle body 102 via an air spring. Each of the bogies has one or two air springs 106 mounted in the same position as an axle 108 in a longitudinal direction of the vehicle body and symmetrically in a width direction of the vehicle. An example of the present invention illustrates a case with one air spring.
The bogie 104 comprises an axle housing 111 arranged in the width direction of the vehicle, the axle 108 housed in the axle housing 111, rubber tires arranged on both sides of the axle 108, an axle frame 112 fixed to the axle housing to support the axle housing 111, and a guide frame 118 mounted on the axle frame 112 and supporting guide wheels 114 and 116 on an edge side of the vehicle 104 in the width direction. The vehicle 100 travels on a guideway T by the guide wheels 114 and 116 being guided by a guide rail not shown in the drawings.
As illustrated in FIG. 6, a suspension frame 120 protruding downward is fixed to the vehicle body 102 and four parallel links 122 and 124 are supported pivotally on the suspension frame 120 by one end thereof. A base part 121 is integral with the suspension frame 120 and fixed under the vehicle body. The axle frame 112 is fixed to the bogie side. The air spring 106 is installed between the base part 121 and the axle frame 112.
The parallel links 122 and 124 are pivotally supported on the axle frame 112 by the other end thereof. The axle 108 is supported by a parallel link mechanism 126 formed by the parallel links 122 and 124 such that the axle 108 can move in a parallel manner in the vertical direction. In this manner, the height fluctuation of the air spring 106 is tolerated. A propeller shaft 109 is connected to the axle 108 so as to transmit the rotation of a drive motor to the rubber tires 110 via an input shaft, a hypoid gear, deferential gear and the axle 108.
A compressed-air tank 128 as a supply source of compressed air, a compressed-air supply pipe 130 for supplying the compressed air from the tank 128 to the air spring 106, and a leveling valve 132 installed in the supply pipe 130 are provided under the vehicle body 102. The leveling valve 132 has a rotating lever 134 which is connected to a valving element of the leveling valve 132.
The leveling valve 132 is mounted on the vehicle body side and houses a valving element such as a rotary valve therein. The rotation shaft 136 is integral with the valving element and protrudes outside of a casing of the leveling valve 132. The rotating lever 134 is connected to the rotation shaft. One end of the rotating lever 134 is connected to an adjusting rod 138 and a pin disposed in a vertical direction and the other end thereof is connected to the axle 108. The adjusting rod 138 is configured such that the length thereof can be adjusted by a means such as a turnbuckle.
Moreover, the air spring 106, the leveling valve 132, the adjusting rod 138 and the like are arranged symmetrically about a centerline O.
With the structure above, when the weight of the vehicle body increases due to passengers boarding, the air spring 106 is compressed and the vehicle body 102 lowers and the space between the vehicle body 102 and the bogie 104 becomes smaller. On the other hand, a tip of the rotating lever 134 is connected to the adjusting rod 138 and thus the rotating lever 134 does not move downward but rotate upward about the rotation shaft 136. The rotating lever 134 tilts upward so as to open the leveling valve 132 and then the compressed air is supplied to the air spring 106 via the compressed-air tank 128. In this manner, the vehicle body 102 is lifted. Once the rotating lever 134 becomes horizontal due to the lift of the vehicle body 102, the leveling valve 132 closes and the vehicle body 102 stops lifting.
When the weight of the vehicle body decreases, the vehicle body moves upward and the rotating lever 134 is tilted downward about the rotation shaft 136 so as to open the leveling valve 132 and discharge the compressed air from the air spring 106. In this manner, the vehicle body 102 lowers and the rotating lever 134 becomes horizontal. When the rotating lever becomes horizontal, the leveling valve 132 closes and the vehicle body 102 stops lowering.
This type of the height adjusting mechanism is disclosed in FIG. 6 and FIG. 7 of Patent Document 1 (JP2000-280900) or FIG. 10 of Patent Document 2 (JP2006-62512).
The air springs are arranged on both sides of the vehicle body in the width direction near the axle. The leveling valve is normally provided for each of the air springs in vicinity thereof. The leveling valve is aligned with the air spring in the longitudinal direction of the vehicle so as to make controlling the tilt in the width direction easier.
As described above, the rotating lever 134 tilts and then the leveling valve opens to open the compressed-air supply pipe 130. To take measures against the hunting of the valving element, a dead-band of the tilt amount is provided in the lower limit area. For instance, the dead-band may be 0 mm to ±4 mm at the tip of the rotating lever. Accordingly, the tilt of the vehicle body is tolerated in the range of the dead-band.
In the guideway-type vehicle equipped with the rubber tires, the position of the leveling valve is restricted in a center area of the width direction inside the rubber tires so as not to obstruct the rubber tires. Therefore, the height fluctuation outside of the rubber tires is much greater in the dead-band. Specifically, even when the height fluctuation is 4 mm at the position where the leveling valve is installed, the height fluctuation outside the rubber tires in the width direction may be around 10 mm and exceed the allowable value of the level difference between the vehicle body and a platform.
In the case of the vehicle having the leveling valves on the front bogie and rear bogie, when the tilt of the adjusting valve at the front bogie is opposite to that at the rear bogie in the range of the dead-band, a twisting moment is generated in the vehicle. As for the vehicle of the new transit system whose distance is short between the front and the rear bogies, the vehicle body is tilted to either one of the sides instead of being twisted. This causes an imbalance between the height of the air spring and the pressure of the compressed air. As a result, the relationship of the actual weight of the vehicle body and the pressure of the compressed air inside the air spring becomes imbalanced in some bogies.
This can send a wrong information to a load-compensating device which calculates the weight of the vehicle body from the pressure of the compressed air in the air spring and controls an accelerating force and a break force of the vehicle, resulting in causing negative effects to speed control and stopping accuracy of the vehicle. It is possible to narrow the dead-band of the leveling valve to solve the issue. However, this causes more frequent hunting of the valve and the structure of the leveling valve becomes complex and expensive.
It is also possible to use a shorter rotating lever 134 so as to increase the sensitivity of the rotating lever which moves the adjusting rod 138 in the vertical direction. However, in the case of the vehicle with the rubber tires, the installation location of the leveling valves is restricted to the center area in the width direction as mentioned above and thus the sensitivity cannot be sufficiently improved with respect to the tilt of the vehicle in the width direction thereof. Therefore, this does not solve the issue.